1. Our Genetic Code

2. Genetic code
It is the sequence of bases (code) that determines what protein is made.
A sequence of bases that code for a protein is called a gene.
A gene can be a few hundred bases to more than 2 million bases (portion of a DNA molecule)
Who knows how this is done?
3 bases make a codon

3. Genes – Please add to your notes
A gene is a short section of the DNA molecule that contains the instructions to make a specific protein.
An organism’s genome is its complete set of genes

4. The Human Genome Project
Mapped three billion base pairs in the human genome
Aim to identify all the genes in the human genome
To develop faster methods for sequencing DNA
finished in 2001
The project involved scientists from 18 different countries 

5. Karyotype
A Karyotype is the number and visual appearance of the chromosomes in the cell nuclei of an organism.

6. What is the importance of proteins?
Proteins are molecules that all the cells of the body need in order to work properly:
Proteins determine the characteristics of the organism. Eg. Hair and eye colour.
Some proteins carry out cell functions: enzymes, hormones
Other proteins are parts of cell structures: cell membrane.
Humans have as many as proteins.

7. Where are proteins made?
Proteins are made in the cytoplasm of the cell by ribosomes.
Ribosomes are made in the nucleolus and then move to the cytoplasm.

8. How does the code become protein?
Gene Expression: DNA Transcription and Translation

9. Video Amoeba Sisters Protein Synthesis

12. Gene Expression is the process of translating of our genetic code into protein.
Occurs in two steps: Transcription and Translation

13. Transcription
Proteins are made in the cytoplasm by ribosomes but DNA never leaves the nucleus.
How does the message get to the cytoplasm?
By a process called transcription.

14. DNA TRANSCRIPTION
When a particular protein is needed, the section of DNA that codes for that protein (gene) is copied and taken out of the nucleus and into the cytoplasm to the ribosomes. This process is called Transcription.
Transcription is the first step in “gene expression” (creating a protein).

15. DNA Transcription: Copying the message in 3 steps
The section of DNA containing the gene of interest unwinds
The message is copied by mRNA (messenger RNA)
mRNA then leaves nucleus and carries the “message” to the ribosomes in the cytoplasm.

17. What is RNA? RNA is ribonucleic acid
Like DNA, it is also a strand of nucleic acids except:
it is single-stranded,
instead of thymine it uses Uracil to pair with adenine.
It’s sugar is ribose instead of deoxyribose
mRNA is called messenger RNA because it takes the copied message out to the ribosomes to make protein.

18. Video
Amoeba Sisters – RNA

19. Transcription: the process of copying the message

20. How does the message become a protein?
Translation is the process in which the sequence of bases on the RNA is “read” by ribosomes to build a protein.
Translation is the second step in “gene expression” (protein formation).

21. Genetic Code The nitrogenous bases are arranged in groups of 3.
The group of three bases is called a codon.
Each codon codes for a specific amino acid
Amino acids are the building blocks of proteins.
Different sequences of amino acids form different proteins.

22. Translation
Once the RNA is in the cytoplasm, a ribosome binds to the RNA and ‘reads” the sequence codons (3 bases).
The ribosome moves down the RNA strand, adding an amino acid for each corresponding codon, creating an amino acid chain.

24. Homework
CYU p47 # 8-15

25. Gene Expression

26. DNA is in our chromosomes
Recall that DNA exists as thread-like material called chromatin but condenses into visible chromosomes just before a cell is ready to divide.
Chromosomes are long, coiled strands of DNA molecules that contain all or part of an organisms genetic material.
What is DNA?
What is the function of DNA?
How is sexual reproduction different from asexual reproduction?

27. How is DNA related to chromosomes?
Chromosomes exist in pairs
Humans have 23 pairs of chromosomes
When an organism reproduces, copies of its chromosomes (DNA) are transferred to the offspring.
What is DNA?
What is the function of DNA?
How is sexual reproduction different from asexual reproduction?

28. Karyotype
A Karyotype is the number and visual appearance of the chromosomes in the cell nuclei of an organism.